Current digital video systems usually provides a frame buffer memory for storing the video graphics signal to be displayed. The video graphics signal generally comes from decompressed video through either broadcasting or networking schemes. This frame buffer memory is essential since it is impractical to decompress and display the same data at the same time. If the video resolution gets higher, that is, the data size is increased in a great amount, a large frame buffer memory is required and the hardware cost will increase.
Conventional methods of overcoming the large memory requirement are to down-sample the decompressed graphics signal then interpolate in output end. For example, horizontal sub-sample one of every two pixels will halve the required memory space. These kind of methods of using interpolation process will blur the output images and therefore degrade the resolution performance. The same result takes place if vertical rather than horizontal sub-sampling is used.
Consequently, one object of the present invention is to provide a compressing/decompressing apparatus and method for compressing and decompressing a video graphics signal in a video system having a frame buffer memory and a display. The apparatus can effectively reduces the memory size while preserves high video resolution of the output images.
Besides, in the compressing/decompressing apparatus of the present invention, a predictor is used to provide an adjusted value for compensating the compressed pixel and therefore improves video resolution of the output images.